The report also failed to explain why NHS managers had given ministers what turned out to be incorrect information.

Professor Beasley said: "I am asking the NHS to do more to ensure that when there is no choice but to mix patients, that more safeguards are taken to ensure that privacy is maintained."

Health Secretary Patricia Hewitt said: "The NHS overall has an excellent record of treating people with dignity and respect.

"However, this report shows there is clearly still more work for the NHS to do to meet our commitment to eliminate mixed-sex accommodation wherever possible."

Katherine Murphy, of the Patients Association, said: "Patients have a right to be treated in a safe environment with privacy, respect and dignity.

"Patients continue to complain and for years politicians have promised to rectify this problem.

"After more than 10 years of promises broken by a succession of ministers, it is time for action."

The Patient Forums organisation said a survey it carried out of 2,500 patients in March this year found 25% had shared a ward or bay with members of the opposite sex.

Chair Jacquie Pearce-Gervis said: "We would like to see an eradication of mixed sex wards in order for all patients to spend their time in hospital recovering and not worrying that their dignity or privacy could be compromised."

Shadow health secretary Andrew Lansley accused the government of trying to bury bad news by publishing the report on the day Tony Blair was expected to announce his resignation.

"Labour will never learn that the public are fed up with their style of government instead of dealing with the problems being faced by patients."